1. Field of the Invention
The present invention relates to walk-behind lawnmowers for cutting grass. In particular the invention relates to safety improvements for mowers incorporating a shredder or chipper, and/or catcher.
2. Summary of the Prior Art
Push-behind or walk-behind lawnmowers with a powered cutting mechanism are well-known. Mowers of this type normally include a generally centrally located deck or housing that has an integral side wall which runs around the perimeter of a generally horizontally oriented deck or housing, and which is aligned substantially vertically running downwards towards the ground. The mower also has a powered cutting mechanism such as a pair of rotating blades, or a plurality of blades, located under the deck and inside the integral side wall. Items such as the engine or power source for the blades are generally located above the deck, attached to the top of the deck. The area bounded by the deck and side wall generally forms a cutting area under the mower.
Mowers usually also include a clippings catcher which catches cut grass clippings. This is normally located at the rear of the mower, attached to the rear of the deck or housing.
While so-called hover mowers are known, such as those produced by ‘Flymo’, most mowers also include wheels, usually located at the four corners of the deck.
Generally, there are two main ways in which mowers can be powered—electrically or by a petrol motor. Electric mowers are usually powered by an electrical cable connected between the mower and a mains outlet. Electric mowers can also be powered by a battery mounted on the machine. Petrol powered mowers are generally known as motor mowers, with the motor included as part of the mower so the mower is self-contained or self-sufficient.
It is common for the cutting mechanism to be formed as a disc that includes at least a pair of cutting blades, aligned at 180 degrees to one another to rotate around a central point, the tips of the blades forming a cutting circle or cutting disc as they rotate. Other types of blade mounting arrangements are also employed, such as the so-called bar blade where both ends of a single bar are sharpened to form cutting edges. The power for the cutting mechanism is provided from a power source. The power source is generally located on top of the deck (e.g. the motor), and a drive shaft extends downwards through the deck to power the cutting blades. For ‘push’ type or user-propelled mowers of either the electric or motor mower type, a user is required to push the mower in order to move it in the direction in which they wish to proceed—the power source does not provide movement power for the mower as a whole, just the cutting mechanism.
However, for some mowers, such as the ‘Masport® series 19 MSV 550 self-propelled’, power is also drawn from the motor in order to propel the mower forwards, a user controlling the movement direction of the mower by exerting sideways pressure on the handle, and the speed of both the mower and (if required) the blades by way of controls on the mower handle. Mowers of this type are generally known as self-propelled mowers.
As the mower moves forward, the tips of the blades contact the grass and cut it. The motion of the blades flings the grass clippings around the inside of the mower cutting area under the deck and towards the rear of the mower in a slingshot effect. The Masport® series 19 mowers are designed to take advantage of this effect, by having a deck with an overall volute shape, with one side of the deck formed as an expanding funnel. The motion of the blades causes the grass clippings and the surrounding air to be channelled along this funnel and out of the rear of the mower. In order to maximise this effect and to increase efficiency it is important that this channel is smooth and that there are no internal impediments which might disrupt the air flow or prevent the grass clippings from being thrown to the rear of the mower.
As well as cutting grass, some types of mowers may also be adapted to dispose of heavier garden waste or garden refuse such as a small branches or similar. This is useful where a user may not require a dedicated static chipper/shredder unit such as are known in the industry, but where the user may encounter circumstances or situations where as well as cutting the grass, they need to quickly and easily deal with or dispose of other, heavier types of garden refuse such as small windfall branches or similar. It is known to incorporate a small chipper or shredder into push mowers so that a user can achieve this. An example of a push mower that incorporates a chipper/shredder would be the ‘Masport® series 19 MSV 3′N′1 Combo’. This is a user-propelled or ‘push’ type mower that includes a chipper shredder. A chipper tube is located on the top of the housing, aligned upwards and angled slightly backwards towards the mower handle. If a user needs to dispose of garden refuse such as small branches or similar, these are dropped or pushed into the top of the tube, passing down the tube into the cutting area under the housing and side wall. The ‘Masport® series 19 MSV 3′N′1 Combo’ includes a second, heavier, bar blade located above the grass cutting blade, with both cutting systems powered by a single drive shaft directly connected to the motor which is located on top of the housing, so that the grass cutting blades and the chipping blades rotate around a single axis. Refuse passing down the tube and entering the cutting area will contact the heavier chipping blades first. This refuse is chipped or shredded by the upper cutting blade or blades, and the resulting chips are disposed of in the same manner as the grass clippings produced by the lower grass cutting blade are disposed of.
In the ‘Masport® series 19 MSV 3′N′1 Combo, clippings are disposed of by being flung or thrown by the cutting blades around the outside perimeter of the cutting space in a centrifugal manner in a similar manner to the way grass clippings are disposed of as outlined above. In order to aid in this disposal and centrifugal style throwing of clippings, the interior space under the deck and side wall (the cutting area) is volute-shaped in the Masport® Series 19 mowers. The mower deck includes an exit aperture at the rear to which a catcher can be connected in use. The chippings and grass clippings are flung around the outside perimeter of the cutting space and through this aperture. With a catcher connected to the rear of the mower, the chippings and grass clippings are collected in the catcher.
For mowers which include a chipper/shredder, where both the grass cutting blades and the chipper blades are arranged to rotate about a single axis, it is highly desirable that the deck is configured in such a manner that the rotation of the blades will sweep grass clippings and chippings around the cutting space and then into a collector, grass catcher or similar. In the Masport® Series 19 mowers, this is achieved by shaping the deck as a volute, as noted above, with an exit aperture extending across the rear of the mower. The clippings and chippings are swept in a circular motion around the volute and then flung backwards (and possibly slightly sideways across the mower from one side to the other), through the exit aperture and then (usually but not necessarily) into a collector at the rear.
Push type mowers that include a chipper/shredder for the disposal of heavier garden waste such as small windfall branches are known, as outlined above. The chipper/shredder blades on these combination mowers tend to be heavier than mower blades, and it is important that as far as practical, users are protected and prevented from being able to place themselves in a position of danger.
In general, the height of the mower above the ground (the ‘ride height’ or ‘cutting height’) can be adjusted. This is usually achieved by adjusting the deck and associated elements (i.e. the engine and the blades) relative to the wheels. This usually means that the size of the gap between the lower edge of the side wall and the ground changes.
It is also desirable in mowers to create ‘rake’. That is, a change in the size of the gap between the front and the rear—e.g. a gap of 10 mm between the ground and the lower edge at the front of the mower and a gap of 20 mm at the rear. This allows air to circulate more freely and improves efficiency.
The present application claims priority from two New Zealand provisional applications being: NZ 589942 and NZ590235. Both these specifications are hereby incorporated into the present application by way of reference in their entirety.
U.S. Pat. No. 4,172,351 describes a mower which has a detachable side shield. The purpose of the side shield is to prevent the ejection of items that might cause harm or damage from the interior cutting space under the mower.
U.S. Pat. No. 4,411,125 describes a mower that has a skirt attached to the sidewall. It is stated that the purpose of the skirt is to prevent debris from being thrown from the housing.
In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.